JP2019092365A5 - - Google Patents

Description

DC pulse power supply

The present invention relates to a DC pulse power supply device that generates a pulsed direct current.

Magnetic confinement fusion experimental equipment requires a strong magnetic field to confine the plasma.
A magnetic field is obtained by passing a current through a magnetic field coil in which a copper wire is wound many times, but in order to obtain a strong magnetic field, it is necessary to pass a large current. Since magnetic energy is stored in the magnetic field coil, the power supply supplies that energy . In addition , energization is short due to the limitation from the temperature rise of the electric wire due to the electric current. A short-time pulsed large current DC and a high voltage power supply for excitation are required. Therefore, a high-voltage DC pulse power supply device that stores energy is required to drive the magnetic field device.

Conventionally, in such a pulsed large current power supply, a large number of capacitors are arranged in series in parallel to form a large capacitor bank, energy is stored as energy of an electric field, and the energy is discharged to a coil to obtain a pulsed large current. .. Capacitors that perform such rapid discharges have a limited number of discharges, with tens of thousands to thousands of discharges, and when the capacitor is destroyed due to an internal short circuit, the capacitor bank. Since all the energy of the capacitor is concentrated and discharged to the faulty capacitor , the energy is explosively released in microseconds, a large current flows in a short time, and it is destroyed by its electromagnetic force and heat. Further, in general, electrostatic energy has a low stored energy density, and it is difficult for electrostatic energy to have an energy amount exceeding several MJ on a large scale. The remaining life of recent advanced film capacitors can be predicted by the change in capacitance, but the number of charge / discharge cycles is the same. In addition, a high-voltage power supply is required to charge the capacitor, and while it is being charged, problems with withstand voltage occur, and there is a long time that a short circuit or ground fault accident that causes discharge destruction may occur, resulting in human electric shock during standby. The possibility of an accident also increases.

Other methods for obtaining a pulsed large current as a synthetic test methods, such as power breaker, requires short alternating large current, which as a test method to generate a short time by short-circuiting the synchronous generator from the prior There was a short-circuit generator method. Called, it is a short-circuit test site, allowed to generate an AC voltage to rotate the synchronous generator, to generate a short-circuit current through the output switch. Here short time damper winding of the generator itself stored energy of the field in the rotational moment of maintaining the field magnetic flux is between a few 10mS number 100 mS, it can be taken out a large current, synchronous short generator method using the generator control of the excitation, the current value in such control of the closing phase and changes a control device bulky so ing, not a simple capacitor bank type substitute for DC pulse power supply.

Japanese Unexamined Patent Publication No. 2003-235179 Japanese Unexamined Patent Publication No. 2000-358344

For example, field coil assumed here is the toroidal field coils of the tokamak type nuclear fusion experimental devices, inductance 44MH, DC resistance 0.14, current is 2.26k A. The electric power is about several hundred kW, the energizing time is about 0.5 seconds, and the required electric power energy is 400 kJ. If this is obtained from the capacitor bank, the installation area will be considerably large. For example, a 3.5kV-4600uF-28kJ capacitor has a size of about 500 × 300 × 950 mm, and 28 capacitors of about 800kJ are required to release 70% of the charged voltage and half of the energy.

I would like to pay attention to the flywheel here. The energy stored in the rotational moment of the flywheel is large , and even a steel flywheel directly connected to the general-purpose 55 kW induction motor with a vertical shaft in FIG. 4 becomes an energy storage device of 220 kJ when rotated at a rated speed of 1500 rpm.
The short-circuit generator of the conventional short-circuit test site is a synchronous generator. As in the example of the short-circuit test of the synchronous generator, the time constant for maintaining the voltage is the time constant Td'' of the damper winding, the time constant for maintaining the magnetic field current is short, and the field magnetic flux is 100 mS or less. Is attenuated, that is, a large amount of power can be obtained only by a short pulse operation.

It is known that an induction motor becomes an induction generator by a self-exciting phenomenon if a phase-advancing current is supplied. In Patent Document 1, an induction motor combined with a flywheel is used to back up in the event of a power failure. In Patent Document 1, the induction machine is idling near the synchronous speed, and the frequency of the backup power decreases as the rotation speed decreases. There is a problem, and if the voltage is maintained, there is no problem with short-term power outages and momentary lows, but it is necessary to prepare a large flywheel as a countermeasure against frequency reduction.

The present invention provides a safe, long-life DC pulse high power in a compact device as a power source for a magnetic field generator, in place of a short-life, high-voltage, short-circuit-risk capacitor bank. Make it an issue.

In the present invention, an induction motor equipped with a fly wheel is rotated at high speed and self-excited by a phase-advancing current of a capacitor, and at the same time, the output voltage is controlled, and the AC power is converted into DC by a diode rectifier or the like to be a DC pulse power supply. It is characterized by being a device .

Since the DC pulse power supply device of the present invention stores energy by the rotation of the flywheel, there is no concern about electric shock, and there is an advantage that a general-purpose induction motor can be used with a long life and a small size.

It is explanatory drawing which showed the circuit of the DC pulse power supply device using the induction machine with a flywheel. (Example 1) It is explanatory drawing which showed the circuit of the DC pulse power supply device which used the transformer with the tap which changes the DC voltage when energized by connecting two induction machines with a flywheel in parallel. (Example 2) This is the experimental result of the self-excitation phenomenon by the induction motor with a 55kW flywheel. Waveforms of DC current (A) and voltage output (V), and DC power output waveform (kW). (1) is the overall waveform. (2) is obtained by shows an enlarged waveform of the time direction. It is a photograph which shows the appearance of the 55kW induction motor with a flywheel of 220kJ-1500rpm.

The DC pulse power supply device using the flywheel inducer according to the present invention is a substitute for a power supply using a conventional capacitor bank as an energy source for pulse-driving the magnetic field generator of the fusion experimental device.

FIG. 1 is a circuit diagram of a first embodiment of the present invention, in which reference numeral 3 indicates an inverter for driving an induction motor 1 , and the inverter 3 obtains DC power from a distribution system or the like to induce. The electric motor 1 is driven from the start to the maximum speed and stands by there. Since it is assumed that it takes about several minutes to 10 minutes to re-accelerate the flywheel 2 after the pulse output , the power received from the distribution system is a slight increment. The motor of the inverter 3 is controlled by a control device (not shown) that controls the rotation speed, constant power, and output voltage. After the acceleration is completed, the inverter 3 is supplied with phase-advancing power to maintain the voltage. var Compensator) is preferably Ru is an operation, briefly, at the end of acceleration, although not shown it is possible in that the generator to shut off all three phase output of the inverter 3 in the AC switch 7 .. Similarly, although not shown, a control device that controls and monitors the entire system such as rotation speed, voltage and current is required.

Flywheel 2 is here rotating steel flywheel at atmospheric pressure, even if the idle loss slightly larger, the power of the experimental apparatus is no problem because the short operating time. According to Patent Document 2, since the idle loss becomes one third at atmospheric pressure helium, if the operation time span long time, should employ this technique. The flywheel 2 that rotates at high speed is operated in the high vacuum vessel 9, but requires the power of a vacuum pump (not shown) to maintain the vacuum, and rotates near the synchronous speed of the generator in helium atmospheric pressure. The operating power of the steel flywheel is low. (Claim 3)
Reference numeral 1 in FIG. 1 indicates a general-purpose induction motor. In the present invention, the generator is not an expensive synchronous generator but a "cage-type induction motor" generally available on the market from 1 kW to about 1000 kW as a generator. adopt. If the phase-advancing capacitor 4 is connected in parallel, the induction motor 1 becomes an induction generator by a self-excited phenomenon. There is also a report that the efficiency as an induction generator is about 2% better than that of a synchronous generator of the same capacity.

The capacity of the phase-advancing capacitor 4 needs to be determined by the power generation output and frequency, and even if it is a fixed phase-advancing capacitor, it will be stable due to the saturation phenomenon of the excitation of the inducer even if it is a little too large. It is sufficient as a power source for the toroidal magnetic field coil of the tokamak fusion experimental device that operates.

AC power generated by the induction motor 1 is converted into DC by the diode rectifier 5 to power the field coil is the load 6. Since the diode rectifier 5 is energized for a short time of about 0.5 seconds, it does not require a cooling device and is compact.

The second embodiment is a further development example of the present invention. As shown in FIG. 2, there is a transformer 8 that changes the AC voltage in front of the diode rectifier 5 , and the voltage is changed according to the load. Since the tap change is performed by the high-speed switching switch 7, it is possible to control the DC output voltage during energization. Since the toroidal magnetic field coil has a time constant of nearly 0.5 seconds, constant control of the coil current and flat top are sufficiently possible with control of several tens of mS.

Since the induction machine is power sharing in proportion to the slip frequency, can be operated in parallel, in FIG. 2, the induction machine 1 and the flywheel 2 indicates a parallel connection of two, electrically plurality The capacity of both power and energy can be increased simply by connecting the two in parallel. Further, in FIG. 2, the gas for the flywheel described in Patent Document 2, which reduces the wind damage of the flywheel 2 and the inducer 1 , cools, and has an electrical withstand voltage, that is, the atmospheric pressure obtained by mixing air with helium. A closed container 9 for sealing in the gas of the above is also shown.

FIG. 3 shows the results of a demonstration experiment of pulsed DC power output by a vertical shaft type induction motor 55 kW in which a 220 kJ, 1500 rpm flywheel shown in FIG. 4 is directly connected to the shaft. In the experiment, when there is no load, it is possible to output a DC voltage by self-exciting with a phase-advancing capacitor, and when the switch is turned on, a DC output is generated via a diode rectifier, and the time constant is 0. It shows that a direct current that decays in about 5 seconds can be generated. This indicates that the induction motor can produce a transient output that is more than twice the rated value.

In industry, a large pulsed direct current is often used in addition to the magnetic field generator. For example, electric discharge machines and spot welding use capacitor discharge as a pulse current source. Further, when an inverter that repeats a pulse operation for a short time uses a voltage source capacitor as an energy source, the charging and discharging of the capacitor generates heat and has a short life, and the number of discharges is limited. Of particular concern is the life of capacitors, which often ends in a fire or explosive event. If the flywheel inducer of the present invention is used as an energy source here as well, there is no limit to the number of repetitions within the range of the rated torque, and the energy is stored in the flywheel. It is safe because there is no discharge destruction accident.

1 Induction motor (squirrel-cage induction motor)
2 Flywheel 3 Inverter 4 Phase-advancing capacitor 5 Diode rectifier 6 Magnetic field coil 7 Switch or high-speed switch 8 Transformer or tapped transformer 9 Sealed container

Claims (4)

Connect a phase advance capacitor to the terminals of the induction motor to be rotated by the flywheel, the self-excitation phenomenon without the induction generator to generate AC power by the DC pulse power supply device for obtaining a DC output through rectifier from AC output. The DC pulse power supply device according to claim 1, wherein the AC output of the induction generator is controlled by switching the tap of the transformer to control the output DC voltage and current. The DC pulse power supply device according to claim 1, which is housed in a closed container and filled with a mixed gas of atmospheric pressure of helium and air in order to reduce wind damage of an inducer that rotates in combination with a flywheel. .. The DC pulse power supply device according to claim 1, wherein a plurality of induction motors with flywheels are electrically connected in parallel in order to increase pulse power and energy.